The following generally relates to sanding machines and, more particularly, relates to a sanding machine having a mechanism for clamping a burnishing element such as sand paper.
Sanding machines are power tools which are commonly used to burnish the surface of a workpiece, particularly to make the surface smooth and even. Generally, a sanding machine comprises a housing and a bottom plate mounted thereunder. A motor is arranged in the housing and drives the bottom plate to move via a transmission mechanism. Both ends of the bottom plate are arranged with a clamping mechanism. A burnishing element, such as a sand paper, could be supported on the lower surface of the bottom plate where the sand paper is clamped by the two clamping mechanisms respectively positioned on both ends of the bottom plate. Thus, the sand paper can be moved along with the bottom plate so as to burnish the surface of the workpiece.
In order to improve the sanding efficiency and quality of sanding machines, a sand paper clamping mechanism with tensioning function is provided in the prior art. For example, U.S. Pat. No. 6,857,948 discloses this kind of the clamping mechanism, which is mounted on one end of the bottom plate and comprises an active jaw and a passive jaw. Both the active jaw and the passive jaw are pivotable together about a shaft in the end of the bottom plate. During mounting of the sand paper, one end of the sand paper is clamped firstly. Next, the other end of the sand paper is put into the clearance between the active jaw and the passive jaw. Then, the active jaw is pivoted to make it close toward the passive jaw so as to clamp the ends of the sand paper between the active and passive jaws. With a further pivoting of the active jaw, it will drive the passive jaw to pivot together. Thus, the end of the sand paper clamped between the two jaws will pivot about the shaft along with the jaws so that it moves away from the other end of the sand paper and is tensioned.
Although the above sand paper clamping mechanism adds a tensioning function it still suffers from at least one defect. For example, because the active and passive jaws of the above clamping mechanism are both mounted on the bottom plate in a movable manner, the vibration of the machine will cause the active and passive jaws to move, so that the clamping and tensioning force between the two jaws is weakened, thus resulting in the clamping and tensioning of the sand paper being unreliable.